1. Field of the Invention
The present invention relates to a fogging device for introducing water and/or vapor into an intake air flow of a gas turbine and to a method of increasing the power output of a gas turbine.
2. Discussion of Background
It is known that the feeding of water or vapor or other suitable liquids or mixtures of liquids into the working medium of a gas turbine can be used to increase the power output which can be produced by a gas turbine. On the one hand, the additional power output is made possible in this case by the cooling effect of fed water, this cooling effect allowing greater firing of the gas turbine. On the other hand, by the feeding of water or vapor, the mass flow which passes the turbine blades is increased, and thus the power output is also increased.
In this case, water can be fed either in the form of vapor, i.e. in the form of air wetting, or else in the form of small water droplets. In other words, water can be fed above the saturation limit. This technique, which is known as over-fogging, is normally carried out by small liquid droplets of a certain size being fed to the air flow which is directed into the compressor (what is referred to as “wet compression”). This technique allows the available power output of the gas turbine″to be increased, since the work required for compressing the inlet air is reduced. This is due to the fact that the evaporation energy of the inlet air flow cools the latter when it passes the compressor stages.
There are a multiplicity of documents which describe this “wet compression” in connection with gas turbines. Thus, for example, U.S. Pat. No. 5,930,990 and its continuation-in-part, U.S. Pat. No. 5,867,977, both of which describe an apparatus and a method for increasing the power output of a gas turbine using wet compression. On the other hand, WO 00/50739 describes a special device for monitoring destructive wet compression, i.e. a device which monitors the gas turbine distortions occurring in this method and if need be correspondingly controls the feeding of water. Another document in this connection is U.S. Pat. No. 6,216,443, in which a device with which small liquid droplets are introduced into the inlet air flow of the compressor is likewise described, this introduction being effected between compressor and downstream of a silencer. The droplets which are fed to the air flow have in this case a specific droplet size of between 1 to 50 micrometers. Another publication from the same applicant, U.S. Pat. No. 6,378,284, the parent application for said U.S. Pat. No. 6,216,443, describes a gas turbine in which liquid droplets are added to the air flow upstream of the compressor, the liquid droplets at least partly evaporating before the inlet into the compressor and thus cooling the air flow and then completely evaporating in the compressor with further cooling of the air flow. In this case, the liquid droplets are introduced into the air flow downstream of an inlet plate having air slots, behind which an air filter or a silencer is normally also arranged.